Haakon is due to travel to Japan next week and the palace said he would still visit Tokyo from June 1 to June 3, but was cancelling a visit to the city of Hachinohe on June 4.

Mette-Marit was diagnosed in 2018 with a rare form of pulmonary fibrosis that causes breathing difficulties, which has repeatedly forced her to take sick leave or scale back her official duties.

Haakon said Tuesday that Mette Marit’s health had worsened recently and that he was “worried”.

The princess has recently appeared in public with a breathing tube connected to an oxygen device carried by a palace employee.

The palace announced in December that the princess might need a lung transplant.

Mette-Marit, who married Haakon in 2001, has had a difficult few months in the spotlight.

Documents were released in January revealing her friendship and frequent contact with convicted US sex offender Jeffrey Epstein between 2011 and 2014.

In addition, her son from a previous relationship, Marius Borg Hoiby, went on trial earlier this year for rape, which he denies.